Materials called metal organic structures known as MOF's (Metal Organic Frameworks) are a novel class of materials because they have high porosity, various topologies and which atomic structure is formed of inorganic coordination subunits, of type MO-yx (where M=Zn, Cu, Fe, Cr, etc.) which are linked by organic ligands or “linkers” that shared multiple complexing functions (e.g. carboxylates, phosphonates, etc.), which increases a unique variety of potential interactions within pores. These interactions rise from clusters of cations MX+-O that normally have unsaturations and which can eventually generate acidic or Lewis basic sites, and on the other hand are found unsaturated or aromatic rings forming ligands and that may create interactions of kind π. Therefore these materials offer great potential both scientific and technological due to combination of features from their fragments, both organic and inorganic, whose main feature is the large specific area (up to 10,000 m2/g) which can potentially develop, thus have been considered as promising materials for applications in magnetic, optical and electronic devices, catalysis, separation, gas storage, molecular recognition, and lastly in processes of selective adsorption of nitrogen molecules present in streams to the diesel production.
The first report of synthesis of a MOF, MOF-5 (Zn), was made by Hailian Li, et al. Design and synthesis of an exceptionally stable and highly porous metal-organic framework. Letters to Nature 402 (1999) 276-279, which states that said material remains crystalline and stable, which is evidenced by X-ray analysis of single crystal, when fully desolvated and calcined at a temperature of 300° C. This synthesis was achieved by sharing ideas from chemistry metal clusters and carboxylates, where a dicarboxylic ligand used in a reaction that provide super-tetrahedral clusters when are covered with monocarboxylates. Rigid and divergent character of added ligand allow joint of clusters in a three dimensional structure resulting in a structure with a large surface area and pore volume greater than that of the porous crystalline zeolites. This simple and potentially universal, synthesis strategy has been used for the preparation of new phases and composites, especially for gas storage application. MOF-5 is formed by Zn-BDC (1,4-benzenedicarboxilate), with final formula of Zn4O(BDC)3.(DMF)8(C6H3Cl).
MOF called MIL-101-Cr (Cr(III) terephthalate) was originally synthesized by Férey G., et al. A Chromium-Based Solid Terephthalate With Unusually Large Pore Volumes and Surface Area. Science 309, 2040 (2005). This MOF has the particularity of developing major Langmuir surface areas (4,500-5,500 m2/g), pore size (29-34 Å) and cell volume (702,000 Å3). The synthesis of MOF known as MIL-101-Cr comprises reacting terephthalic acid (H2BDC, 166 mg, 1 mmol) with chromium nitrate (Cr(NO3)3.9H2O, 400 mg, 1 mmol), hydrofluoric acid (HF, 0.2 ml, 1 mmol) and water (H2O, 4.8 mL, 265 mmol), under hydrothermal conditions for 8 hours at 220° C. This hydrothermal reaction produces chromium terephthalate highly crystallized green powder with formula Cr3F(H2O)2O[(O2C)—C6H4—(CO2)3]3.nH2O (where n≈25) based on chemical analysis. The chromium-based yield is ≈50%. The special feature of this synthesis is using hydrofluoric acid (HF) during preparation.
Subsequently, Jiangfeng Yang, et al. Synthesis of metal-organic framework MIL-101 in TMAOH-Cr(NO3)3-H2BDC-H2O and Its hydrogen-storage behavior. Microporous and Mesoporous Materials 130 (2010) 174-179, performed the synthesis of MOF MIL-101-Cr, replacing the HF by different alkali; potassium hydroxide (KOH), tetramethylammonium hydroxide (TMAOH), triethylamine ((C2H5)3N), dimethylamine (C2H7N), methylamine (CH5N) and ammonia (NH3) to prevent recrystallization of terephthalic acid (H2DBC). As a result, it was found that more stable material and with structure type MOF MIL-101-Cr was called TMAOH-Cr(NO3)3-H2BDC-H2O.
This type of MOF (MOF MIL-101-Cr) has a zeolite structure consisting of two chambers quasi-spherical cages (2.9 and 3.4 nm) accessible through windows 1.2 and 1.6 nm, as MOF Fe-MIL-101. Both materials have large surfaces and pore volumes (usually, from 3,200 to 3,900 and 1.4 to 2.1 m2g−1, respectively), also have very good resistance to common solvents and thermal stability (Fe-MIL-101 up to 180° C. and Cr-MIL-101 up to 300° C.). The atomic structure MIL-101 consists of terephthalate molecule that acts as ligand of M3O-carboxylate trimers (M=Fe or Cr). These metal ions are octahedrally coordinated with water molecules in the linking terminals. It has been reported that water molecules (two water molecules per trimeric group according to elemental and thermogravimetric analysis) can be easily eliminated by thermal treatment under vacuum, thus providing coordinately unsaturated and catalytically active sites (Young Kyu Hwang, et al. Selective sulfoxidation of aryl sulfides by coordinatively unsaturated metal centers in chromium carboxylate MIL-101. Applied Catalysis A: General 358 (2009) 249-253.
In order to establish the state of the art of the MOF MIL-101, a literature review of patents was made based on the researcher who discovered and reported the material MOF MIL-101-Cr Ferey Gerard Institut Lavoisier, CNRS Unite Mixte Material for Research, University of Versailles St-Quentin, Versailles Cedex, France.
We found that the MOF material called MIL-101-Cr only appears with this name:                Above-mentioned article by Férey G., et al. A Chromium-Based Solid Terephthalate With Unusually Large Pore Volumes and Surface Area. Science 309, 2040 (2005).        In patent application US 2009/0131703 A1, May 21, 2009, Jhung et al., claim a preparing method of porous inorganic-organic hybrid materials called Cr-BDCA-1, BDCA where is 1,4-dibenzocarboxylilic acid or also known as terephthalic acid. This preparation method is basically that reported by Férey G., et al. A Chromium-Based Solid Terephthalate With Unusually Large Pore Volumes and Surface Area. Science 309, 2040 (2005), already mentioned, which uses HF, being main difference using ultrasound for 1 min to homogenize the reaction mixture and then using a microwave oven to quickly heat reaction at 210° C. and reduce the reaction time to 3 min.        In patent application US 2010/0273642 A1, Oct. 28, 2010, Chang et al., referred to a method to functionalized porous organic-inorganic hybrid materials, especially MOF MIL-101-Cr or mesoporous organic-inorganic materials, particularly mesoporous material SBA-15. Functionalizing organic substances are related to inorganic substances, ionic liquids, and organic-inorganic hybrid substances incorporated step by step in inorganic unsaturated sites instead of hydroxyl groups for application in catalysis, adsorbents, gas storage materials, sensors, membranes, thin films and catalyst supports.        In the patent application US 2011/0172412 A1, Jul. 14, 2011, Serre et al., claim the use of the MOF MIL-101-Fe as a material prone to be reduced, to take advantage of reduced Fe to separate molecules mixtures with different unsaturation degree with a selectivity such that it can be adjusted by controlling the reduction degree of MOF MIL-101-Fe.        In the patent application US 2012/0165183 A1, Jun. 28, 2012, Chang et al., claim the synthesis of MOF MIL-101-Cr without using hydrofluoric acid, so consider it a synthesis more environmentally friendly. It also shows that the material obtained by this method has the same crystallinity than MOF MIL-101-Cr prepared by the method using hydrofluoric acid.        
The state of the art known to the applicant, represented mainly by the technologies described in the patent documents referred, obviously exceeded by the present invention, as in said prior art there is no processes to obtaining MOF materials MIL-101-Cr and MOF MIL-101-Cr-MX+ where MX+ can be any metal cation, such as Mg2+, Al3+ or Ti4+, employing for its synthesis metal epoxides and alkoxides, avoiding the use of hydrofluoric acid (HF) or bases as synthesis controlling agents.
It is therefore an object of the present invention to provide a process for obtaining materials MOF MIL-101-Cr and MOF MIL-101-Cr-MX+ where MX+ can be any metal cation, such as Mg2+, Al3+ or Ti4+, employing for its synthesis metal epoxides and alkoxides, avoiding the use of hydrofluoric acid (HF) or bases as synthesis controlling agents.
It is another object of the present invention to provide a process for obtaining MOF materials MIL-101-Cr and MOF MIL-101-Cr-MX+ where MX+ can be any metal cation, such as Mg2+, Al3+ or Ti4+, 100% pure, with controlled mesoporosity associated with a hysteresis P/P0 from 0.7 to 0.99, BET surface area from 2,500 to 3,500 m2/g, pore volume from 1.1 to 2.2 cm3/g, and pore diameter from 15 to 55 nm.